Pde10 inhibitors and related compositions and methods

ABSTRACT

Compounds that inhibit PDE10 are disclosed that have utility in the treatment of a variety of conditions, including (but not limited to) psychotic, anxiety, movement disorders and/or neurological disorders such as Parkinson&#39;s disease, Huntington&#39;s disease, Alzheimer&#39;s disease, encephalitis, phobias, epilepsy, aphasia, Bell&#39;s palsy, cerebral palsy, sleep disorders, pain, Tourette&#39;s syndrome, schizophrenia, delusional disorders, drug-induced psychosis and panic and obsessive-compulsive disorders. Pharmaceutically acceptable salts, stereoisomers, solvates and prodrugs of the compounds are also provided. Also disclosed are compositions containing a compound in combination with a pharmaceutically acceptable carrier, as well as methods relating to the use thereof for inhibiting PDE10 in a warm-blooded animal in need of the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/742,199, filed Jan. 15, 2013, now pending, which is a divisional ofU.S. patent application Ser. No. 12/535,598, filed Aug. 4, 2009, nowissued U.S. Pat. No. 8,377,930, which claims the benefit under 35 U.S.C.§ 119(e) of U.S. Provisional Patent Application No. 61/086,406, filedAug. 5, 2008, U.S. Provisional Patent Application No. 61/118,088, filedNov. 26, 2008, and U.S. Provisional Patent Application No. 61/218,311,filed Jun. 18, 2009, which applications are incorporated herein byreference in their entireties.

BACKGROUND Technical Field

This invention relates generally to compounds having activity as PDE10inhibitors, and to compositions containing the same, as well as tomethods of treating various disorders by administration of suchcompounds to a warm-blooded animal in need thereof.

Description of the Related Art

Cyclic nucleotide phosphodiesterases (PDEs) are represented by a largesuperfamily of enzymes. PDEs are known to possess a modulararchitecture, with a conserved catalytic domain proximal to the carboxylterminus, and regulatory domains or motifs often near the aminoterminus. The PDE superfamily currently includes more than twentydifferent genes subgrouped into eleven PDE families (Lugnier, C.,“Cyclic nucleotide phosphodiesterase (PDE) superfamily: a new target forthe development of specific therapeutic agents.” Pharmacol Ther. 2006March; 109(3):366-98).

A recently described PDE, PDE10, was reported simultaneously by threeindependent groups (Fujishige et al., “Cloning and characterization of anovel human phosphodiesterase that hydrolyzes both cAMP and cGMP(PDE10A),” J Biol Chem 1999, 274:18438-18445; Loughney et al.,“Isolation and characterization of PDE10A, a novel human 3′, 5′-cyclicnucleotide phosphodiesterase,” Gene 1999, 234:109-117; Soderling et al.,“Isolation and characterization of a dual-substrate phosphodiesterasegene family: PDE10A,” Proc Natl Acad Sci USA 1999, 96:7071-7076). PDE10has the capacity to hydrolyze both cAMP and cGMP; however, the K_(m) forcAMP is approximately 0.05 whereas the K_(M) for cGMP is 3 μM. Inaddition, the V_(max) for cAMP hydrolysis is fivefold lower than forcGMP. Because of these kinetics, cGMP hydrolysis by PDE10 is potentlyinhibited by cAMP in vitro, suggesting that PDE10 may function as acAMP-inhibited cGMP phosphodiesterase in vivo. Unlike PDE8 or PDE9,PDE10 is inhibited by IBMX with an IC₅₀ (50% inhibitory concentration)of 2.6 μM. (See Soderling and Beavo, “Regulation of cAMP and cGMPsignaling: new phosphodiesterases and new functions,” Current Opinion inCell Biology, 2000, 12:174-179.)

PDE10 contains two amino-terminal domains that are similar to thecGMP-binding domains of PDE2, PDE5 and PDE6, which are domains conservedacross a wide variety of proteins. Because of the wide conservation ofthis domain, it is now referred to as the GAF domain (for the GAFproteins: cGMP binding phosphodiesterases; the cynobacterial Anabaenaadenylyl cyclase; and the Escherichia coli transcriptional regulatorfhlA). Although in PDE2, PDE5 and PDE6 the GAF domains bind cGMP, thisis probably not the primary function of this domain in all cases (e.g.,E. coli are not thought to synthesize cGMP). Interestingly, in vitrobinding studies of PDE10 indicate the dissociation constant (K_(d)) forcGMP binding is well above 9 μM. As in vivo concentrations of cGMP arenot thought to reach such high levels in most cells, it seems likelythat either the affinity of PDE10 for cGMP is increased by regulation,or that the primary function of the GAF domain in PDE10 may be forsomething other than cGMP binding.

Inhibitors of the PDE family of enzymes have widely been sought for abroad indication of therapeutic uses. Reported therapeutic uses of PDEinhibitors include allergies, obtrusive lung disease, hypertension,renal carcinoma, angina, congestive heart failure, depression anderectile dysfunction (WO 01/41807 A2). Other inhibitors of PDE have beendisclosed for treatment of ischemic heart conditions (U.S. Pat. No.5,693,652). More specifically, inhibitors of PDE10 have been disclosedfor treatment of certain neurological and psychiatric disordersincluding, Parkinson's disease, Huntington's disease, schizophrenia,delusional disorders, drug-induced psychosis and panic andobsessive-compulsive disorders (U.S. Patent Application No.2003/0032579). PDE10 has been shown to be present at high levels inneurons in areas of the brain that are closely associated with manyneurological and psychiatric disorders. By inhibiting PDE10 activity,levels of cAMP and cGMP are increased within neurons, and the ability ofthese neurons to function properly is thereby improved. Thus, inhibitionof PDE10 is believed to be useful in the treatment of a wide variety ofconditions or disorders that would benefit from increasing levels ofcAMP and cGMP within neurons, including those neurological, psychotic,anxiety and/or movement disorders mentioned above.

While advances have been made with regard to inhibition of PDE10, thereremains a need in the field for inhibitors of PDE10, as well as the needto treat various conditions and/or disorders that would benefit from thesame.

BRIEF SUMMARY

In brief, this invention is generally directed to compounds that haveactivity as PDE10 inhibitors, as well as to methods for theirpreparation and use, and to pharmaceutical compositions containing thesame.

In one embodiment, the compounds have the following general structure(I):

including pharmaceutically acceptable salts, stereoisomers, solvates andprodrugs thereof, wherein X, R₁, R₂, R₃, R₄ and R₅ are as defined below.

In another embodiment, the compounds have the following generalstructure (IV):

including pharmaceutically acceptable salts, stereoisomers, solvates andprodrugs thereof, wherein R₁, R₂, R₃, R₄ and R₅ are as defined below.

The compounds of this invention have utility over a wide range oftherapeutic applications, and may be used to treat a wide variety ofconditions or disorders that would benefit from increasing levels ofcAMP and cGMP, especially within neurons, including (but not limited to)neurological disorders, such as psychotic disorders, anxiety disorders,movement disorders and/or neurological disorders such as Parkinson'sdisease, Huntington's disease, Alzheimer's disease, encephalitis,phobias, epilepsy, aphasia, Bell's palsy, cerebral palsy, sleepdisorders, pain, Tourette's syndrome, schizophrenia, delusionaldisorders, bipolar disorders, post-traumatic stress disorders,drug-induced psychosis, panic disorders, obsessive-compulsive disorders,attention-deficit disorders, disruptive behavior disorders, autism,depression, dementia, cognitive disorders, epilepsy, insomnias andmultiple sclerosis.

The methods of this invention include administering an effective amountof a compound of the foregoing structures, typically in the form of apharmaceutical composition, to a mammal in need thereof, including ahuman. Thus, in a further embodiment, pharmaceutical compositions aredisclosed containing one or more compounds of the foregoing structuresin combination with a pharmaceutically acceptable carrier or diluent.

These and other aspects of the invention will be apparent upon referenceto the following detailed description. To this end, various referencesare set forth herein which describe in more detail certain backgroundinformation, procedures, compounds and/or compositions, and are eachhereby incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates that Compound 12-63 of the present invention (asidentified in Table 1 of Example 12) significantly reduces hyperactivityof mice in a psychostimulant (PCP)-induced model of psychosis ascompared to vehicle control.

FIG. 2 illustrates that Compound 12-55 of the present invention (asidentified in Table 1 of Example 12) significantly reduces hyperactivityof mice in the PCP-induced model of psychosis as compared to vehiclecontrol.

FIG. 3 illustrates that Compound 12-60 of the present invention (asidentified in Table 1 of Example 12) significantly reduces hyperactivityof mice in the PCP-induced model of psychosis as compared to vehiclecontrol.

FIG. 4 illustrates that Compound 12-44 of the present invention (asidentified in Table 1 of Example 12) significantly reduces a conditionedavoidance response (CAR) in mice trained in a CAR model of psychosis ascompared to vehicle control.

FIGS. 5A and 5B illustrate that Compound 12-63 of the present invention(as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis as comparedto vehicle control (FIG. 5A) and significantly reduces a conditionedavoidance response (CAR) in mice trained in a CAR model of psychosis ascompared to vehicle control (FIG. 5B).

FIGS. 6A and 6B illustrate that Compound 12-104 of the present invention(as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis as comparedto vehicle control (FIG. 6A) and significantly reduces a conditionedavoidance response (CAR) in mice trained in a CAR model of psychosis ascompared to vehicle control (FIG. 6B).

FIGS. 7A and 7B illustrate that Compound 12-114 of the present invention(as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis as comparedto vehicle control (FIG. 7A) and significantly reduces a conditionedavoidance response (CAR) in mice trained in a CAR model of psychosis ascompared to vehicle control (FIG. 7B).

FIGS. 8A and 8B illustrate that Compound 12-132 of the present invention(as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis as comparedto vehicle control (FIG. 8A) and significantly reduces a conditionedavoidance response (CAR) in mice trained in a CAR model of psychosis ascompared to vehicle control (FIG. 8B).

FIGS. 9A and 9B illustrate that Compound 12-134 of the present invention(as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis, indose-dependent fashion, as compared to vehicle control (FIG. 9A) andsignificantly reduces a conditioned avoidance response (CAR) in micetrained in a CAR model of psychosis, in dose-dependent fashion, ascompared to vehicle control (FIG. 9B).

FIGS. 10A and 10B illustrate that Compound 12-115 of the presentinvention (as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis, in adose-dependent fashion, as compared to vehicle control (FIG. 10A) andsignificantly reduces a conditioned avoidance response (CAR) in micetrained in a CAR model of psychosis as compared to vehicle control (FIG.10B).

FIGS. 11A and 11B illustrate that Compound 12-140 of the presentinvention (as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis, in adose-dependent fashion, as compared to vehicle control (FIG. 11A) andsignificantly reduces a conditioned avoidance response (CAR) in micetrained in a CAR model of psychosis, in a dose-dependent fashion, ascompared to vehicle control (FIG. 11B).

FIGS. 12A and 12B illustrate that Compound 12-142 of the presentinvention (as identified in Table 1 of Example 12) significantly reduceshyperactivity of mice in the PCP-induced model of psychosis as comparedto vehicle control (FIG. 12A) and significantly reduces a conditionedavoidance response (CAR) in mice trained in a CAR model of psychosis ascompared to vehicle control (FIG. 12B).

DETAILED DESCRIPTION

As mentioned above, the present invention is directed generally tocompounds useful as PDE10 inhibitors, as well as to methods for theirpreparation and use, and to pharmaceutical compositions containing thesame.

In one embodiment, the PDE10 inhibitors have the following structure(I):

or a pharmaceutically acceptable salt, stereoisomer, solvate or prodrugthereof,

wherein:

-   -   X is —O— or —S—;    -   R₁ is C₁₋₆alkyl, C₁₋₆haloalkyl, C₁₋₆aralkyl, aryl,        (CH₂)_(n)O(CH₂)_(m)CH₃ or —(CH₂)_(n)N(CH₃)₂;    -   R₂ and R₃ are the same or different and independently        substituted or unsubstituted heterocyclyl, or substituted or        unsubstituted aryl;    -   R₄ and R₅ are the same or different and independently hydrogen,        C₁₋₆alkyl or C₁₋₆haloalkyl;    -   n is 1, 2, 3, 4, 5 or 6; and    -   m is 0, 1, 2, 3, 4, 5 or 6.

In another embodiment, the PDE10 inhibitors have the following structure(IV):

or a pharmaceutically acceptable salt, stereoisomer, solvate or prodrugthereof,

wherein:

-   -   R₁ is hydrogen, C₁₋₆alkyl, C₁₋₆haloalkyl, C₁₋₆aralkyl, aryl,        (CH₂)_(n)O(CH₂)_(m)CH₃ or —(CH₂)_(n)N(CH₃)₂;    -   R₂ is substituted or unsubstituted aryl;    -   R₃ is substituted or unsubstituted heterocyclyl, or substituted        or unsubstituted aryl; and    -   R₄ and R₅ are the same or different and independently hydrogen,        C₁₋₆alkyl or C₁₋₆haloalkyl;    -   n is 1, 2, 3, 4, 5 or 6; and    -   m is 0, 1, 2, 3, 4, 5 or 6.

As used herein, the above terms have the following meaning:

“Amino” refers to the —NH₂ radical.

“Cyano” refers to the —CN radical.

“Hydroxy” or “hydroxyl” refers to the —OH radical.

“Imino” refers to the ═NH substituent.

“Nitro” refers to the —NO₂ radical.

“Oxo” refers to the ═O substituent.

“Thioxo” refers to the ═S substituent.

“C₁₋₆alkyl” means a straight chain or branched, noncyclic or cyclic,unsaturated or saturated aliphatic hydrocarbon radical containing from 1to 6 carbon atoms. Representative saturated straight chain alkylsinclude methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, and thelike; while saturated branched alkyls include isopropyl, sec-butyl,isobutyl, tert-butyl, isopentyl, and the like. Representative saturatedcyclic alkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,and the like; while unsaturated cyclic alkyls include cyclopentenyl andcyclohexenyl, and the like. Unsaturated alkyls contain at least onedouble or triple bond between adjacent carbon atoms (referred to as an“alkenyl” or “alkynyl”, respectively). Representative straight chain andbranched alkenyls include ethylenyl, propylenyl, 1-butenyl, 2-butenyl,isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl,2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, and the like; whilerepresentative straight chain and branched alkynyls include acetylenyl,propynyl, 1-butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl,3-methyl-1-butynyl, and the like.

“C₁₋₆alkylene” or “C₁₋₆alkylene chain” refers to a straight or brancheddivalent hydrocarbon chain linking the rest of the molecule to a radicalgroup, consisting solely of carbon and hydrogen, which is saturated orunsaturated (i.e., contains one or more double and/or triple bonds), andhaving from one to six carbon atoms, e.g., methylene, ethylene,propylene, n-butylene, ethenylene, propenylene, n-butenylene,propynylene, n-butynylene, and the like. The alkylene chain is attachedto the rest of the molecule through a single or double bond and to theradical group through a single or double bond. The points of attachmentof the alkylene chain to the rest of the molecule and to the radicalgroup can be through one carbon or any two carbons within the chain.

“C₁₋₆alkoxy” refers to a radical of the formula —OR_(a) where R_(a) isan alkyl radical as defined above, for example, methoxy, ethoxy and thelike.

“Aryl” means a hydrocarbon ring system radical comprising hydrogen, 6 to18 carbon atoms and at least one aromatic ring. The aryl radical may bea monocyclic, bicyclic, tricyclic or tetracyclic ring system, which mayinclude fused or bridged ring systems. Aryl radicals include, but arenot limited to, aryl radicals derived from aceanthrylene,acenaphthylene, acephenanthrylene, anthracene, azulene, benzene,chrysene, fluoranthene, fluorene, as-indacene, s-indacene, indane,indene, naphthalene, phenalene, phenanthrene, pleiadene, pyrene, andtriphenylene.

“C₁₋₆aralkyl” means a radical of the formula —R_(b)-R_(c) where R_(b) isan alkylene chain as defined above and R_(c) is one or more arylradicals as defined above, for example, benzyl, diphenylmethyl and thelike.

“Cycloalkyl” or “carbocyclic ring” refers to a stable non-aromaticmonocyclic or polycyclic hydrocarbon radical consisting solely of carbonand hydrogen atoms, which may include fused or bridged ring systems,having from three to fifteen carbon atoms, preferably having from threeto ten carbon atoms, and which is saturated or unsaturated and attachedto the rest of the molecule by a single bond. Monocyclic radicalsinclude, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl, and cyclooctyl. Polycyclic radicals include, for example,adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo[2.2.1]heptanyl,and the like.

“Halo” or “halogen” refers to bromo, chloro, fluoro or iodo.

“C₁₋₆haloalkyl” refers to a C₁₋₆alkyl radical, as defined above, that issubstituted by one or more halo radicals, as defined above, e.g.,trifluoromethyl, difluoromethyl, trichloromethyl, 2,2,2-trifluoroethyl,1,2-difluoroethyl, 3-bromo-2-fluoropropyl, 1,2-dibromoethyl, and thelike.

“Heterocycle” or “heterocyclyl” means a 4- to 7-membered monocyclic, or7- to 10-membered bicyclic, heterocyclic ring which is either saturated,unsaturated or aromatic, and which contains from 1 to 4 heteroatomsindependently selected from nitrogen, oxygen and sulfur, and wherein thenitrogen and sulfur heteroatoms may be optionally oxidized, and thenitrogen heteroatom may be optionally quaternized, including bicyclicrings in which any of the above heterocycles are fused to a benzenering. The heterocycle may be attached via any heteroatom or carbon atom.An aromatic heterocycle is referred to herein as a “heteroaryl”, andincludes (but is not limited to) furyl, benzofuranyl, thiophenyl,benzothiophenyl, pyrrolyl, indolyl, isoindolyl, azaindolyl, pyridyl,quinolinyl, isoquinolinyl, oxazolyl, isooxazolyl, benzoxazolyl,pyrazolyl, imidazolyl, benzimidazolyl, thiazolyl, benzothiazolyl,isothiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl,cinnolinyl, phthalazinyl, oxadiazolyl, thiadiazolyl, benzisoxazolyl,triazolyl, tetrazolyl, indazolyl and quinazolinyl. In addition to theheteroaryls listed above, heterocycles also include morpholinyl,pyrrolidinonyl, pyrrolidinyl, piperidinyl, piperazinyl, and the like. Inaddition, heterocycles also include benzothiophen-2-yl,2,3-dihydrobenzo-1,4-dioxin-6-yl, benzo-1,3-dioxol-5-yl and the like.

The term “substituted” as used herein (for example, in the context of asubstituted heterocyclyl or substituted aryl) means that at least onehydrogen atom is replaced with a substituent. “Substituents” within thecontext of this invention include halogen, hydroxy, oxo, cyano, nitro,imino, thioxo, amino, alkylamino, dialkylamino, alkyl, alkoxy,alkylthio, haloalkyl, aryl, aralkyl, heteroaryl, heteroarylalkyl,heterocycle and heterocyclealkyl, as well as —NR_(a)R_(b),—NR_(a)C(═O)R_(b), —NR_(a)C(═O)NR_(a)NR_(b),—NR_(a)C(═O)OR_(b)—NR_(a)SO₂R_(b), —C(═O)R_(a), —C(═O)OR_(a),—C(═O)NR_(a)R_(b), —OC(═O)NR_(a)R_(b), —OR_(a), —SR_(a), —SOR_(a),—S(═O)₂R_(a), —OS(═O)₂R_(a), —S(═O)₂OR_(a), ═NSO₂R_(a) and—SO₂NR_(a)R_(b). In the foregoing, R_(a) and R_(b) in this context maybe the same or different and independently hydrogen, alkyl, haloalkyl,cycloalkyl, aryl, aralkyl, heterocyclyl. In addition, the foregoingsubstituents may be further substituted with one or more of the abovesubstituents.

In further embodiments of structure (I), X is —O— and the compound hasthe following structure (II):

In more specific embodiments of structure (II):

-   -   R₁ is C₁₋₆alkyl, C₁₋₆haloalkyl, C₁₋₆aralkyl, aryl,        (CH₂)_(n)O(CH₂)_(m)CH₃ or —(CH₂)_(n)N(CH₃)₂;    -   R₂ is substituted or unsubtituted heterocyclyl, substituted        phenyl, or substituted or unsubstituted naphthyl;    -   R₃ is substituted or unsubstituted heterocyclyl, or substituted        or unsubstituted aryl; and    -   R₄ and R₅ are the same or different and independently hydrogen,        C₁. 6alkyl or C₁₋₆haloalkyl;    -   n is 1, 2, 3, 4, 5 or 6; and    -   m is 0, 1, 2, 3, 4, 5 or 6.

In further more specific embodiments of structure (II), R₄ and R₅ arethe same or different and independently hydrogen or C₁₋₆alkyl (such as,for example, hydrogen), R₁ is C₁₋₆alkyl (such as, for example, methyl,ethyl or isopropyl), R₃ is substituted phenyl (such as, for example,3,4,5-trimethoxyphenyl or 4-bromo-3,5-dimethoxyphenyl) and/or R₂ issubstituted or unsubstituted phenyl (such as, for example,4-morpholinophenyl or 4-(1H-pyrazol-1-yl)phenyl), substituted orunsubstituted naphthyl, or substituted or unsubstituted heteroaryl.

In other further embodiments of structure (I), X is —S— and the compoundhas the following structure (III):

In more specific embodiments of structure (III):

-   -   R₁ is C₁₋₆alkyl, C₁₋₆haloalkyl, —(CH₂)_(n)O(CH₂)_(m)CH₃ or        (CH₂)_(n)N(CH₃)₂,

R₂ and R₃ are the same or different and independently substituted orunsubstituted heterocyclyl, or substituted or unsubstituted aryl; and

-   -   R₄ and R₅ are the same or different and independently hydrogen,        C₁₋₆alkyl or C₁₋₆haloalkyl;    -   n is 1, 2, 3, 4, 5 or 6; and    -   m is 0, 1, 2, 3, 4, 5 or 6.

In further more specific embodiments of structure (III), R₄ and R₅ arethe same or different and independently hydrogen or C₁₋₆alkyl (such as,for example, hydrogen), R₁ is C₁₋₆alkyl (such as, for example, methyl,ethyl or isopropyl), R₃ is substituted phenyl (such as, for example,3,4,5-trimethoxyphenyl or 4-bromo-3,5-dimethoxyphenyl) and/or R₂ issubstituted or unsubstituted phenyl (such as, for example,4-morpholinophenyl or 4-(1H-pyrazol-1-yl)phenyl), substituted orunsubstituted naphthyl, or substituted or unsubstituted heteroaryl.

In more specific embodiments of structure (IV):

-   -   R₁ is hydrogen, C₁₋₆alkyl, C₁₋₆haloalkyl, C₁₋₆aralkyl, aryl,        (CH₂)_(n)O(CH₂)_(m)CH₃ or —(CH₂)_(n)N(CH₃)₂;    -   R₂ is

-   -    wherein        -   R_(2a) is —N(R_(2b)R_(2c)) or a heterocyclic ring containing            at least one N ring atom, and        -   R_(2b) and R_(2c) are the same or different and            independently hydrogen, C₁₋₆alkyl, C₁₋₆haloalkyl,            C₁₋₆aralkyl or aryl;    -   R₃ is

-   -    wherein        -   R_(3a) is —C₁₋₆alkoxy,        -   R_(3b) is halogen, and        -   R_(3c) is —C₁₋₆alkoxy;    -   R₄ and R₅ are the same or different and independently hydrogen,        C₁₋₆alkyl or C₁₋₆haloalkyl;    -   n is 1, 2, 3, 4, 5 or 6; and    -   m is 0, 1, 2, 3, 4, 5 or 6.

In other more specific embodiments of structure (IV):

-   -   R₁ is hydrogen, C₁₋₆alkyl, C₁₋₆haloalkyl, C₁₋₆aralkyl, aryl,        (CH₂)_(n)O(CH₂)_(m)CH₃ or —(CH₂)_(n)N(CH₃)₂;    -   R₂ is

-   -    wherein        -   R_(2a) is —N(R_(2b)R_(2c)) or a heterocyclic ring containing            at least one N ring atom, provided that R_(2a) is not            1H-tetrazol-1-yl, and        -   R_(2b) and R_(2c) are the same or different and            independently hydrogen, C₁₋₆alkyl, C₁₋₆haloalkyl,            C₁₋₆aralkyl or aryl;    -   R₃ is

-   -    wherein        -   R_(3a) is —C₁₋₆alkoxy, and        -   R_(3c) is —C₁₋₆alkoxy;    -   R₄ and R₅ are the same or different and independently hydrogen,        C₁₋₆alkyl or C₁₋₆haloalkyl;    -   n is 1, 2, 3, 4, 5 or 6; and    -   m is 0, 1, 2, 3, 4, 5 or 6.

In other more specific embodiments of structure (IV), R₄ and R₅ arehydrogen or C₁₋₆alkyl (such as, for example, hydrogen), R₁ is hydrogenor C₁₋₆alkyl (such as, for example, methyl, ethyl, isopropyl orcyclopropyl), R₃ is substituted phenyl (such as, for example,3,4,5-trimethoxyphenyl or 4-bromo-3,5-dimethoxyphenyl) and/or R₂ issubstituted or unsubstituted phenyl (such as, for example,4-morpholinophenyl or 4-(1H-pyrazol-1-yl)phenyl) or substituted orunsubstituted naphthyl.

The compounds of the present invention may be prepared by known organicsynthesis techniques, including the methods described in more detail inthe Examples, or in some instances may be obtained from commerciallyavailable sources. In general, the compounds of structures (I) and (IV)above may be made by the following reaction schemes, wherein allsubstituents are as defined above unless indicated otherwise.

Compounds of formula 1 can be obtained commercially or synthesizedthrough standard literature methods. Compounds of formula 1 can bereacted with a variety of alcohols using the method disclosed in U.S.Pat. No. 7,129,238 (which is incorporated herein by reference in itsentirety) to provide compounds of formula 2. Compounds of formula 2 canbe heated with a variety of alcohols under acidic conditions to providecompounds of formula 3. Compounds of formula 3 can then be heated toreflux in the presence of hydrazine hydrate in an alcoholic solvent toprovide compounds of formula 4. Compounds of formula 4 can be reactedwith aldehydes or ketones of formula 5 to provide compounds of structure(II).

Compounds of formula 1 can be obtained commercially or synthesizedthrough standard literature methods. Compounds of formula 1 can bereacted with a variety of halogenating reagents such as NCS to providecompounds of formula 2. Compounds of formula 2 can be reacted witharomatic compounds under Friedel-Crafts conditions to provide compoundsof formula 3. Compounds of formula 3 can then be heated to reflux in thepresence of hydrazine hydrate in an alcoholic solvent to providecompounds of formula 4. Compounds of formula 4 can be reacted withaldehydes or ketones of formula 5 to provide compounds of structure(III).

Compounds of formula 1 can be obtained commercially or synthesizedthrough standard literature methods. Compounds of formula 1 can bereacted with a variety of alcohols under acidic conditions to providecompounds of formula 2. Compounds of formula 2 can be treated with avariety of bases and alkylating reagents to provide compounds of formula3. Compounds of formula 3 can then be heated to reflux in the presenceof hydrazine hydrate in an alcoholic solvent to provide compounds offormula 4. Compounds of formula 4 can be reacted with aldehydes orketones of formula 5 to provide compounds of structure (IV).

The compounds of the present invention may generally be utilized as thefree acid or free base. Alternatively, the compounds of this inventionmay be used in the form of acid or base addition salts. Acid additionsalts of the free amino compounds of the present invention may beprepared by methods well known in the art, and may be formed fromorganic and inorganic acids. Suitable organic acids include maleic,fumaric, benzoic, ascorbic, succinic, methanesulfonic, acetic,trifluoroacetic, oxalic, propionic, tartaric, salicylic, citric,gluconic, lactic, mandelic, cinnamic, aspartic, stearic, palmitic,glycolic, glutamic, and benzenesulfonic acids. Suitable inorganic acidsinclude hydrochloric, hydrobromic, sulfuric, phosphoric, and nitricacids. Base addition salts included those salts that form with thecarboxylate anion and include salts formed with organic and inorganiccations such as those chosen from the alkali and alkaline earth metals(for example, lithium, sodium, potassium, magnesium, barium andcalcium), as well as the ammonium ion and substituted derivativesthereof (for example, dibenzylammonium, benzylammonium,2-hydroxyethylammonium, and the like). Thus, the term “pharmaceuticallyacceptable salt” of structures (I) through (IV) is intended to encompassany and all acceptable salt forms.

In addition, prodrugs are also included within the context of thisinvention. Prodrugs are any covalently bonded carriers that release acompound of structures (I) through (IV) in vivo when such prodrug isadministered to a patient. Prodrugs are generally prepared by modifyingfunctional groups in a way such that the modification is cleaved, eitherby routine manipulation or in vivo, yielding the parent compound.Prodrugs include, for example, compounds of this invention whereinhydroxy, amine or sulfhydryl groups are bonded to any group that, whenadministered to a patient, cleaves to form the hydroxy, amine orsulfhydryl groups. Thus, representative examples of prodrugs include(but are not limited to) acetate, formate and benzoate derivatives ofalcohol and amine functional groups of the compounds of structures (I)through (IV). Further, in the case of a carboxylic acid (—COOH), estersmay be employed, such as methyl esters, ethyl esters, and the like.

In addition, prodrugs having the following structures (I-A), (I-B),(IV-A) and (IV-B) are included within the scope of this invention:

wherein R₁₀ is C₁₋₆alkyl, aryl, —OC₁₋₆alkyl, —O-aryl or —NC₁₋₆alkyl.Enolic prodrugs of structure (I-A) and (IV-A) may be prepared bytreating a compound of structure (I) or structure (IV), respectively,with a base, such as triethylamine, in a solvent, such asdichloromethane, followed by the addition of an electrophile, such asacetyl chloride. N-acylated prodrugs of structure (I-B) and (IV-B) maybe prepared via thermal rearrangement by heating a prodrug of structure(I-A) or (IV-A), respectively, in a solvent, such as toluene. See, e.g.,Carpino et al., J. Org. Chem., 53, 6047-6053 (1988); Geita et al.,Zhurnal Organicheskoi Khimii, 13(7), 1461-1465 (1977) (translationavailable from Institute of Organic Synthesis, Academy of Sciences ofthe Latvian SSR, 1346-1350); Maroulis et al., J. Heterocyclic Chem., 21,1653-1656 (1984); Monge et al., J. Heterocyclic Chem., 21, 397-400(1984); and Singh et al., Tetrahedron Letters, 29, 2711-2714 (1973).

With regard to stereoisomers, the compounds of structures (I) through(IV) may have chiral centers and may occur as racemates, racemicmixtures and as individual enantiomers or diastereomers. All suchisomeric forms are included within the present invention, includingmixtures thereof. Furthermore, some of the crystalline forms of thecompounds of structures (I) through (IV) may exist as polymorphs, whichare included in the present invention. In addition, some of thecompounds of structures (I) through (IV) may also form solvates withwater or other organic solvents. Such solvates are similarly includedwithin the scope of this invention.

In another embodiment of the invention, pharmaceutical compositionscontaining one or more compounds of structures (I) through (IV) aredisclosed. For the purposes of administration, the compounds of thepresent invention may be formulated as pharmaceutical compositions.Pharmaceutical compositions of the present invention comprise one ormore compounds of the present invention and a pharmaceuticallyacceptable carrier and/or diluent. The PDE10 inhibitor is present in thecomposition in an amount which is effective to treat a particulardisorder—that is, in an amount sufficient to achieve desired PDE10inhibition, and preferably with acceptable toxicity to the warm-bloodedanimal. Typically, the pharmaceutical compositions of the presentinvention may include a PDE10 inhibitor in an amount from 0.1 mg to 250mg per dosage depending upon the route of administration, and moretypically from 1 mg to 60 mg. Appropriate concentrations and dosages canbe readily determined by one skilled in the art.

In general terms, a typical daily dosage might range from about 1 μg/kgto 100 mg/kg, preferably 0.01-100 mg/kg, more preferably 0.1-70 mg/kg,depending on the type and severity of the disease whether, for example,by one or more separate administrations. For repeated administrationsover several days or longer, depending on the condition, the treatmentis sustained until a desired suppression of disease symptoms occurs.However, other dosage regimens may be useful. The progress of thistherapy can be monitored by standard techniques and assays. Thespecification for the dosage unit forms of the invention are dictated byand directly dependent on the unique characteristics of the activecompound and the particular therapeutic effect to be achieved, and thelimitations inherent in the art of compounding such an active compoundfor the treatment of individuals.

Pharmaceutically acceptable carrier and/or diluents are familiar tothose skilled in the art. For compositions formulated as liquidsolutions, acceptable carriers and/or diluents include saline andsterile water, and may optionally include antioxidants, buffers,bacteriostats and other common additives. The compositions can also beformulated as pills, capsules, granules, or tablets which contain, inaddition to a PDE10 inhibitor, diluents, dispersing and surface activeagents, binders, and lubricants. One skilled in this art may furtherformulate the PDE10 inhibitor in an appropriate manner, and inaccordance with accepted practices, such as those disclosed inRemington's Pharmaceutical Sciences, Gennaro, Ed., Mack Publishing Co.,Easton, Pa. 1990.

In another embodiment, the present invention provides a method fortreating diseases such as (but not limited to) psychotic disorders,anxiety disorders, movement disorders and/or neurological disorders suchas Parkinson's disease, Huntington's disease, Alzheimer's disease,encephalitis, phobias, epilepsy, aphasia, Bell's palsy, cerebral palsy,sleep disorders, pain, Tourette's syndrome, schizophrenia, delusionaldisorders, bipolar disorders, post-traumatic stress disorders,drug-induced psychosis, panic disorders, obsessive-compulsive disorders,attention-deficit disorders, disruptive behavior disorders, autism,depression, dementia, cognitive disorders, epilepsy, insomnias andmultiple sclerosis as discussed above. Such methods includeadministering of a compound of the present invention to a warm-bloodedanimal in an amount sufficient to treat the condition. In this context,“treat” includes prophylactic administration. Such methods includesystemic administration of a PDE10 inhibitor of this invention,preferably in the form of a pharmaceutical composition as discussedabove. As used herein, systemic administration includes oral andparenteral methods of administration, including subcutaneous,intramuscular, intracranial, intraorbital, ophthalmic, intraventricular,intracapsular, intraarticular, intraspinal, intracisternal,intraperitoneal, intranasal, aerosol, intravenous, intradermal,inhalational, transdermal, transmucosal, and rectal administration.

For oral administration, suitable pharmaceutical compositions of PDE10inhibitors include powders, granules, pills, tablets, and capsules aswell as liquids, syrups, suspensions, and emulsions. These compositionsmay also include flavorants, preservatives, suspending, thickening andemulsifying agents, and other pharmaceutically acceptable additives andexcipients. For parenteral administration, the compounds of the presentinvention can be prepared in aqueous injection solutions which maycontain, in addition to the PDE10 inhibitor, buffers, antioxidants,bacteriostats, and other additives and excipients commonly employed insuch solutions. Compositions of the present invention may be carried ina delivery system to provide for sustained release or enhanced uptake oractivity of the therapeutic compound, such as a liposomal or hydrogelsystem for injection, a microparticle, nanopartical or micelle systemfor oral or parenteral delivery, or a staged capsule system for oraldelivery.

In a further advantage of the present invention, compounds of structures(I) through (IV) are expected to avoid or reduce metabolic side effectsassociated with conventional antipsychotics, in particular the incidenceof therapeutically induced obesity. For example, chronic use ofolanzapine (Zyprexa®), the most widely prescribed medication to treatschizophrenia, and related atypical antipsychotics is associated withsignificant metabolic side effects including obesity and associatedconditions such as diabetes.

In animals, subchronic treatment with olanzapine stimulates food intakeand increases body weight, consistent with human situations.Furthermore, olanzapine acutely lowers blood leptin levels. Leptin is asatiety hormone produced from adipose tissues, and decrease of leptinlevel stimulates appetite. It is theorized that olanzapine couldstimulate food intake at least partly by reducing leptin levels. Acuteadministration of olanzapine also changes the animal's response inglucose and insulin levels in glucose tolerance tests, which may also bedirectly linked to olanzapine's effect in food intake and body weightgain. Examination of the acute effect of PDE10 inhibitors of the presentinvention on metabolism, such as leptin, insulin and glucose changesduring a metabolic challenge in standard animal models, as well as thechronic effect of PDE10 inhibitors of the present invention in foodintake, body weight and energy homeostasis, in comparison witholanzapine should provide evidence to the pharmaceutical advantage ofPDE10 inhibitors as antipsychotics in terms of less side-effectconcerns.

The compositions of the present invention may be administered incombination with one or more additional therapeutic agents, incombination or by concurrent or sequential administration. Suitableadditional agents (i.e., adjuvants) may include typical antipsychoticsthat block dopamine-D₂ receptors and serotonin 5HT₂ receptors, e.g.,haloperidol, fluphenazine, chlorpromazine, and atypical antipsychotics,e.g., clozapine, olanzapine, risperidone, quetiapine, ziprasidone.

Compounds of this invention may be assayed to determine their IC₅₀values by a modification of the two-step method of Thompson and Appleman(Biochemistry 10; 311-316; 1971). In short, cAMP is spiked with (³H)cAMPand incubated with PDE10 and various concentrations of a compound ofstructure (I). After the appropriate incubation time, the reaction isterminated by heating. The mixture is then subjected to treatment withsnake venom phosphatase. The phosphatase hydrolyzes any AMP in themixture, but leaves unreacted cAMP intact. Thus, by separating cAMP fromthe mixture and determining its concentration (by radiography), thepercent of inhibition can be determined. IC₅₀ values can be calculatedby performing the experiment at several concentrations using standardgraphical means. A detailed description of the actual technique used forIC₅₀ assays as set forth in following Examples. To this end, PDE10inhibitors of the invention have an IC₅₀ of 100 μM or less, generallyless than 10 and typically less than 1 μM.

The following examples are provided for purposes of illustration, notlimitation.

EXAMPLES Example 1 Synthesis of(E)-2-Methoxy-2-(naphthalen-2-yl)-N-(3,4,5-trimethoxybenzylidene)acetohydrazide2-Hydroxy-2-(naphthalen-2-yl)acetic acid

A solution of 2-naphthaldehyde (2.0 g, 1.0 eq), benzyltriethylammoniumchloride (BTEAC) (0.13 g), and 50% aqueous NaOH (2.3 mL), andβ-cyclodextrin (0.10 g) in chloroform (10 mL) was heated at 55° C. for12 hours. The mixture was then poured into water and the solution washedwith EtOAc. The aqueous layer was then acidified to pH 1 by dropwiseaddition of HCl (conc.). This was extracted with EtOAc, dried overNa₂SO₄, filtered and concentrated under reduced pressure to yield ayellow oil (0.75 g, 29%) that was not further purified.

Methyl 2-hydroxy-2-(naphthalen-2-yl)acetate

To a stirred solution of 2-hydroxy-2-(naphthalen-2-yl)acetic acid (0.75g, 1 eq) in dry MeOH was added sulfuric acid (0.1 mL) dropwise andheated to reflux. Stirring was then continued for 2 hours. The reactionmixture was then cooled and poured into saturated aqueous NaHCO₃ andextracted with EtOAc. The combined organic fractions were dried overNa₂SO₄, filtered, and concentrated under reduced pressure to yield anoil (0.63 g, 78%) that was not further purified.

Methyl 2-methoxy-2-(naphthalen-2-yl)acetate

To a stirred solution of methyl 2-hydroxy-2-(naphthalen-2-yl)acetate(0.63 g, 1 eq) in dry DMF was added NaH (0.45 g, 4 eq) and methyl iodide(0.74 mL, 4.1 eq). Stirring was then continued for 24 hours. Thereaction mixture was then poured into ethyl acetate and washed with H₂O.The combined organic fractions were dried over Na₂SO₄, filtered, andconcentrated under reduced pressure to yield an oil that was purified bycolumn chromatography using ethyl acetate and hexanes to yield an oil(0.358 g, 53%).

2-Methoxy-2-(naphthalen-2-yl)acetohydrazide

A stirred solution of methyl 2-methoxy-2-(naphthalen-2-yl)acetate (0.358g, 1 eq) and hydrazine hydrate (4 mL) was heated to reflux for 1 hour.The reaction mixture was then cooled and the solvents removed underreduced pressure. The crude oil was diluted with EtOAc and washed withH₂O and the organic phase dried over Na₂SO₄, filtered, and the solventsremoved under reduced pressure to yield a yellow oil (0.17 g, 47%) thatwas used without further purification.

(E)-2-Methoxy-2-(naphthalen-2-yl)-N-(3,4,5-trimethoxybenzylidene)acetohydrazide

In a round-bottom glass flask equipped with a magnetic stir bar methyl2-methoxy-2-(naphthalen-2-yl)acetohydrazide (0.17 g, 1 eq) was dissolvedin ethanol (10 mL) at room temperature. To this well stirred solution,acetic acid (10 mL) and 3,4,5-trimethoxy-benzaldehyde (0.145 g, 1 eq)were added, and the reaction mixture was heated at 90° C. for 2 hours.The mixture was then cooled and the crude product was diluted with Et₂Oand filtered and the solid was washed thoroughly with Et₂O to yield0.176 g, 58% of the product (1-1) as a white solid.

Example 2 Synthesis of(E)-2-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxy-N′-(3,4,5-trimethoxybenzylidene)acetohydrazide 2-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxyaceticacid

To a stirred solution of 2,3-dihydrobenzo[b][1,4]dioxine-6-carbaldehyde(3.0 g, 1.0 eq) and bromoform (2.0 mL, 1.27 eq) in MeOH (18 mL) anddioxane (18 mL) was added dropwise a solution of potassium hydroxide(5.1 g, 5.0 eq) in MeOH (18 mL) over 15 minutes. Stirring was thencontinued for 24 hours. The mixture was then poured into water and thesolution washed with EtOAc and acidified to pH 1 by dropwise addition ofHCl (conc.). This was extracted with EtOAc, dried over Na₂SO₄, filteredand concentrated under reduced pressure to yield a yellow oil (4.1 g)that was not further purified.

Methyl 2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxyacetate

To a stirred solution of2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxyacetic acid (18.3 mmol)in dry MeOH was added sulfuric acid (2.5 mL) dropwise and heated at 90°C. Stirring was then continued for 3 hours. The reaction mixture wasthen cooled and poured into saturated aqueous NaHCO₃ and extracted withEtOAc. The combined organic fractions were dried over Na₂SO₄, filtered,and concentrated under reduced pressure to yield an oil (3.7 g) that wasnot further purified.

2-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxyacetohydrazide

To a stirred solution of methyl2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxyacetate (18.3 mmol) inanhydrous EtOH (150 mL) was added hydrazine hydrate (73.2 mmol, 4 eq)and heated to 90° C. Stirring was then continued for 24 hours. Thereaction mixture was then cooled and the solvents removed under reducedpressure. The crude oil was diluted with EtOAc and washed with H₂O andthe organic phase dried over Na₂SO₄, filtered, and the solvents removedunder reduced pressure to yield a yellow oil (3.5 g) that was usedwithout further purification.

(E)-2-(2,3-Dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxy-N-(3,4,5-trimethoxybenzylidene)acetohydrazide

In a round-bottom glass flask equipped with a magnetic stir bar2-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-2-methoxyacetohydrazide (1 eq.,1.1 mmol; 260 mg) was dissolved in ethanol (10 mL) at room temperature.To this well stirred solution, acetic acid (˜3 drops) and 3, 4,5-trimethoxy-benzaldehyde (1.2 eq, 1.3 mmol; 260 mg) were added, and thereaction mixture was heated for 12 hours. The mixture was then cooledand the crude product was diluted with Et₂O and filtered and the solidwas washed thoroughly with Et₂O to yield: 300 mg (65%) of (2-1).

Example 3 Synthesis of(E)-2,2-Diphenyl-N-(3,4,5-trimethoxybenzylidene)acetohydrazide Methyl2,2-diphenylacetate

To a stirred solution of 2,2-diphenylacetic acid (1 gram, 1 equiv) indry MeOH (50 mL) was added sulfuric acid (0.4 mL) dropwise and heated toreflux. Stirring was then continued for 3 hours. The reaction mixturewas then cooled and poured into saturated aqueous NaHCO₃ and extractedwith EtOAc. The combined organic fractions were dried over Na₂SO₄,filtered, and concentrated under reduced pressure to yield an oil (1.0g, 93%) that was not further purified.

2,2-Diphenylacetohydrazide

To a stirred solution of methyl 2,2-diphenylacetate (0.5 g, 1 equiv) inanhydrous EtOH (150 mL) was added hydrazine hydrate (8 mL) and heated toreflux. Stirring was then continued for 1 hour. The reaction mixture wasthen cooled and the solvents removed under reduced pressure. The crudeoil was diluted with EtOAc and washed with H₂O and the organic phasedried over Na₂SO₄, filtered, and the solvents removed under reducedpressure to yield a yellow oil (0.97 g, 97%) that was used withoutfurther purification.

(E)-2,2-Diphenyl-N-(3,4,5-trimethoxybenzylidene)acetohydrazide

In a round-bottom glass flask equipped with a magnetic stir bar2,2-diphenylacetohydrazide (0.33 g, 1 equiv) was dissolved in ethanol(20 mL) at room temperature. To this well stirred solution, acetic acid(1.4 mL) and 3, 4, 5-trimethoxybenzaldehyde (0.29 g, 1 equiv) wereadded, and the reaction mixture was heated to reflux for 2 hours. Themixture was then cooled and the crude product was diluted with Et₂O andfiltered and the solid was washed thoroughly with Et₂O to yield theproduct (3-1) (0.056 g, 10%).

Example 4 Synthesis of(E)-N-(3,4-Dimethoxybenzylidene)-2-(methylthio)-2-phenylacetohydrazideMethyl 2-chloro-2-(methylthio)acetate

Methyl 2-chloro-2-(methylthio)acetate can be synthesized according toliterature procedures (Boehme, H.; Krack, W.; Justus Liebigs Annalen derChemie; 1977; 51-60. Iwama, Tetsuo; Harutoshi, Matsumoto; Tadashi,Kataoka; Journal of the Chemical Society, Perkin Transactions 1: Organicand Bio-Organic Chemistry (1972-1999); 1997; 835-844).

Methyl 2-(methylthio)-2-phenylacetate

In a round-bottom glass flask equipped with a magnetic stir bar methyl2-chloro-2-(methylthio)acetate (1.3 g, 1 equiv) was dissolved in benzene(20 mL) and aluminum chloride (3.36 g, 2.8 equiv) added in one portionand heated to reflux for 3 hours. The mixture was then cooled and washedwith H₂O, brine, and dried over MgSO₄. The organic layer wasconcentrated under reduced pressure to yield a yellow oil that was usedwithout further purification (0.56 g, 35%).

2-(Methylthio)-2-phenylacetohydrazide

To a stirred solution of methyl 2-(methylthio)-2-phenylacetate (0.300 g,1 equiv) in anhydrous EtOH (5 mL) was added hydrazine hydrate (0.15 mL,2 equiv) and heated to reflux. Stirring was then continued for 18 hours.The reaction mixture was then cooled and the solvents removed underreduced pressure. The crude oil was diluted with EtOAc and washed withH₂O and the organic phase dried over Na₂SO₄, filtered, and the solventsremoved under reduced pressure to yield a yellow oil which was purifiedby flash chromatography on silica gel using ethyl acetate and hexanes.The purified product was a white solid (193 mg, 66%).

(E)-N′-(3,4-Dimethoxybenzylidene)-2-(methylthio)-2-phenylacetohydrazide

In a round-bottom glass flask equipped with a magnetic stir bar2-(methylthio)-2-phenylacetohydrazide (0.132 g, 1 equiv) was dissolvedin ethanol (5 mL) at room temperature. To this well stirred solution,acetic acid (2 drops) and 3, 4-dimethoxybenzaldehyde (0.111 g, 1 equiv)were added, and the reaction mixture was heated to reflux for 12 hours.The mixture was then cooled and the crude product was diluted with Et₂Oand filtered and the solid was washed thoroughly with Et₂O to yield theproduct (4-1) (0.120 g, 52%).

Example 5 Synthesis of (1Z, N′E)-2-Methoxy-2-(naphthalen-1-yl)-N-(3,4,5-trimethoxybenzylidene)acetohydrazonic pivalic anhydride

An oven dried flask was charged with(E)-2-methoxy-2-(naphthalen-1-yl)-N-(3, 4,5-trimethoxybenzylidene)acetohydrazide (0.1 g, 0.25 mmol) (preparedaccording to the foregoing procedures) and put under argon. Anhydrousdichloromethane (20 mL), triethylamine (0.17 mL, 1.2 mmol), and pivaloylchloride (0.081 mL, 0.67 mmol) were added and the mixture was stirred atroom temperature for 18 hours. The mixture was poured into H₂O and theresulting aqueous layer was extracted with dichloromethane twice. Thecombined organics were washed with water and brine, dried over Na₂SO₄,filtered and concentrated in vacuo. Purification by chromatography(ethyl acetate-hexanes) gave the product (5-1) as a light yellow solid(0.12 g, 100%).

Example 6 Synthesis of(E)-2-Methoxy-2-(quinolin-5-yl)-N-(3,4,5-trimethoxybenzylidene)-acetohydrazide

A suspension of quinoline-5-carboxaldehyde (3.12 g, 19.9 mmol) indiethyl ether (42 mL) was cooled over an ice bath. Cold solutions ofNH₄Cl (1.09 g, 18.7 mmol) in water (4.5 mL) and KCN (1.34 g, 20.5 mmol)in water (4.5 mL) were added successively. The mixture was allowed towarm gradually to room temperature with rapid stirring. After 1.75 hourstotal reaction time, the mixture was cooled over an ice bath and the tansolid was collected on a Buchner funnel, rinsed with water, a smallamount of methanol, and diethyl ether. The product was dried undervacuum to give a tan solid (2.6 g, 76% yield). The compound was usedwithout further purification.

A suspension of 2-hydroxy-2-(quinolin-5-yl)acetonitrile (2.56 g, 13.9mmol) in absolute ethanol (70 mL) was cooled over an ice bath. HCl wasbubbled slowly through the mixture for 1 hour then it was stirred for 15minutes over ice. The ice bath was removed and water (5 mL) wascautiously added to the reaction. The mixture was heated at 60° C. for15 minutes, 50° C. for 2 hours, and it was allowed to cool to roomtemperature. Water was added to the reaction mixture and it was madebasic with the slow addition of solid KOH, solid NaHCO₃ and saturatedaqueous NaHCO₃ until the pH=9. The mixture was extracted with EtOActhree times and the combined organics were washed with water and brine,dried over Na₂SO₄ and concentrated in vacuo to give ethyl2-hydroxy-2-(quinolin-5-yl)acetate as a brown oil (2.39 g, 74% yield).

To a solution of ethyl 2-hydroxy-2-(quinolin-5-yl)acetate (1.5 g, 6.5mmol) in anhydrous THF in an oven-dried flask under argon was addediodomethane (1.2 mL, 19.2 mmol) and the mixture was cooled over an icebath. NaH (60% in oil; 0.26 g, 6.5 mmol) was added and the mixturestirred for 1 hour over ice. After removing the ice bath, stirring wascontinued for an additional 3.25 hours, and more NaH (60%; 0.030 g, 0.75mmol) was added. The mixture was stirred for 45 minutes then thereaction was quenched with brine and further diluted with water. Theaqueous mixture was extracted with EtOAc and the combined organics werewashed with water three times, brine once, dried over Na₂SO₄ andconcentrated in vacuo. Purification by chromatography (50%EtOAc-hexanes) gave ethyl 2-methoxy-2-(quinolin-5-yl)acetate as a yellowoil (0.9 g, 57% yield).

To a solution of ethyl 2-methoxy-2-(quinolin-5-yl)acetate (0.9 g, 3.67mmol) in absolute ethanol (25 mL) was added hydrazine hydrate (1.0 mL,20.5 mmol) and the mixture was heated at 85° C. for 18.5 hours. Aftercooling to room temperature, the mixture was poured into ice-water (˜150mL) then concentrated in vacuo. The residue was taken up in EtOAc,washed with diluted brine once, water twice then brine. The organicswere dried over Na₂SO₄ and concentrated in vacuo to give2-methoxy-2-(quinolin-5-yl)acetohydrazide as an off-white foam (0.651 g,77% yield) that was used without further purification.

To a mixture of 2-methoxy-2-(quinolin-5-yl)acetohydrazide (0.149 g, 0.65mmol) and 3, 4, 5-trimethoxybenzaldehyde (0.138 g, 0.70 mmol) inabsolute ethanol (5 mL) was added acetic acid (1 drop). The mixture washeated at 60° C. for 17 hours. After cooling to room temperature, thesolid was collected on a Buchner funnel and rinsed with ethanol anddiethyl ether then dried in vacuo to give(E)-2-methoxy-2-(quinolin-5-yl)-N-(3,4,5-trimethoxybenzylidene)acetohydrazide(6-1) as a white powder (0.197 g, 75% yield).

Example 7 Synthesis of(E)-2-(4-(Dimethylamino)phenyl)-2-methoxy-N-(3,4,5-trimethoxybenzylidene)acetohydrazide

To a suspension of 4-(dimethylamino)benzaldehyde (5.05 g, 33.85 mmol) indiethyl ether (60 mL) in an oven-dried flask under argon was added ZnI₂(0.325 g, 1.0 mmol). Trimethylsilyl cyanide (5.00 mL, 40.0 mmol) wasadded slowly and the mixture was stirred at room temperature for 1.75hours. The solution was diluted with EtOAc and washed with saturatedaqueous NaHCO₃, water and brine then dried over Na₂SO₄. Afterconcentration in vacuo,2-(4-(dimethylamino)phenyl)-2-(trimethylsilyloxy)acetonitrile wasobtained as a grey solid (8.3 g, 99% yield).

To a solution of 2-(4-(dimethylamino)phenyl)-2-(trimethylsilyloxy)acetonitrile (7.19 g, 28.9 mmol) in THF (35 mL) was added 1 M aqueousHCl (1 mL) and the mixture was stirred for 1 hour. Additional 1 M HCl (1mL) was then added and the reaction mixture was stirred for anadditional 50 minutes. The mixture was made basic with solid NaHCO₃ thendiluted with EtOAc and water. The layers were separated and the organicswere washed with saturated aqueous NaHCO₃, water and brine. The solutionwas dried over Na₂SO₄ and concentrated in vacuo to give2-(4-(dimethylamino)phenyl)-2-hydroxyacetonitrile as an off-white solid(5.2 g, quantitative yield). The product was used without furtherpurification.

An ice-cold suspension of2-(4-(dimethylamino)phenyl)-2-hydroxyacetonitrile (5.7 g, 32.3 mmol) inabsolute ethanol (60 mL) was bubbled with HCl for 15 minutes. All solidswent into solution; the ice bath was removed and the mixture stirred for15 minutes. Water (5 mL) was added and the mixture was stirred for 40minutes then heated at 60° C. for 1.5 hours. The mixture was dilutedwith additional water then made basic with the addition of NaHCO₃ untilthe pH was 9-10. The aqueous mixture was extracted with EtOAc twice andthe combined organics were washed with water and brine, dried overNa₂SO₄, vacuum filtered through Celite and concentrated in vacuo.Purification by chromatography (25-50% EtOAc-hexanes) gave ethyl2-(4-(dimethylamino)phenyl)-2-hydroxyacetate as a light yellow solid(2.32 g, 32% yield).

Ethyl 2-(4-(dimethylamino)phenyl)-2-methoxyacetate was synthesized fromethyl 2-(4-(dimethylamino)phenyl)-2-hydroxyacetate according to themethod used for the preparation of Example 6. The product, isolatedafter extractive workup, was an orange oil (0.675 g, 65% yield) and wasused without further purification.

To a solution of ethyl 2-(4-(dimethylamino)phenyl)-2-methoxyacetate(0.675 g, 2.84 mmol) in absolute ethanol (20 mL) was added hydrazinehydrate (0.8 mL, 16.4 mmol) and the mixture was heated at reflux for 22hours. Additional hydrazine hydrate (1.0 mL, 20.6 mmol) was added andthe heating continued for 7 hours. After cooling to room temperature,the mixture was concentrated in vacuo. The residue was dissolved inEtOAc and washed with water and brine, dried over Na₂SO₄ andconcentrated in vacuo. The solid product was stirred with hot diethylether then hexanes were added. After cooling to room temperature, thesolids were collected on a Buchner funnel and rinsed with 50% diethylether-hexanes then dried under vacuum to give2-(4-(dimethylamino)phenyl)-2-methoxyacetohydrazide as an orange solid(0.246 g). Additional product was isolated from the mother liquor bychromatography (80-100% EtOAc-hexanes, then 5% methanol-EtOAc) to givean off-white solid (0.173 g, 66% yield total).

(E)-2-(4-(Dimethylamino)phenyl)-2-methoxy-N-(3,4,5-trimethoxybenzylidene)acetohydrazide was synthesized from2-(4-(dimethylamino)phenyl)-2-methoxyacetohydrazide according to themethod used for the preparation of Example 6. The product (7-1) wasobtained as a white solid (0.0626 g, 34% yield).

Example 8 Synthesis of(E)-2-(Benzo[b]thiophen-2-yl)-2-methoxy-N′-(3,4,5-trimethoxybenzylidene)acetohydrazide

To a solution of benzo[b]thiophene-2-carbaldehyde (2.19 g, 13.5 mmol) inanhydrous THF (200 mL) was added a solution of NaHSO₃ (6.18 g, 59.4mmol) in water (50 mL). KCN (3.248 g, 49.9 mmol) was added and themixture was stirred at room temperature for 22 hours. The reactionmixture was then heated at 45° C. for 1 hour. After cooling to roomtemperature, the mixture was diluted with water and brine and extractedwith EtOAc three times. The combined organics were washed with brine,dried over Na₂SO₄ and concentrated in vacuo. Purification bychromatography (0-25% EtOAc-hexanes) gave2-(benzo[b]thiophen-2-yl)-2-hydroxyacetonitrile as an off-white solid(1.09 g, 46% yield).

A mixture of 2-(benzo[b]thiophen-2-yl)-2-hydroxyacetonitrile (5.76 mmol)in 3 M aqueous HCl (20 mL) and methanol (8 mL) was heated at 60° C. for10 minutes then at 80° C. for 20 hours. Concentrated HCl (10 mL) wasthen added and heating was continued for 5 hours. After cooling to roomtemperature, the volatiles were removed in vacuo. The residue wasextracted with EtOAc and the combined organics were washed with waterand brine, dried over Na₂SO₄ and concentrated in vacuo to give2-(benzo[b]thiophen-2-yl)-2-hydroxyacetic acid as a brown oil (1.20 g)which was used with further purification.

To a solution of 2-(benzo[b]thiophen-2-yl)-2-hydroxyacetic acid (1.20 g,approx. 5.76 mmol) in anhydrous methanol (10 mL) was added concentratedH₂SO₄ (0.25 mL). The mixture was heated at 60° C. for 19 hours. The heatwas increased to 70° C. and stirred for 3.5 hours. After cooling to roomtemperature, the mixture was diluted with water and extracted withEtOAc. The combined organics were washed with dilute aqueous NaHCO₃ andbrine then dried over Na₂SO₄ and concentrated in vacuo. Purification bychromatography (10-25% EtOAc-hexanes) gave methyl2-(benzo[b]thiophen-2-yl)-2-methoxyacetate (0.464 g, 35%).

To a solution of methyl 2-(benzo[b]thiophen-2-yl)-2-methoxyacetate(0.174 g, 0.74 mmol) in absolute ethanol (3 mL) was added hydrazinehydrate (0.14 mL, 2.87 mmol) and the mixture was heated at 50° C. for 20hours. After cooling to room temperature, the solution was concentratedin vacuo. The residue was dissolved in EtOAc and washed with water andbrine, dried over Na₂SO₄ and concentrated in vacuo to give2-(benzo[b]thiophen-2-yl)-2-methoxyacetohydrazide as a colorless oil(0.182 g, quantative yield).

(E)-2-(Benzo[b]thiophen-2-yl)-2-methoxy-N-(3,4,5-trimethoxybenzylidene)acetohydrazide was synthesized from2-(4-(dimethylamino)phenyl)-2-methoxyacetohydrazide according to themethod used for the preparation of Example 6. The product (8-1) wasobtained as a white solid (0.089 g, 60% yield).

Example 9 Synthesis of(E)-N′-(3,4-Dimethoxybenzylidene)-3-methyl-2-phenylbutanehydrazideMethyl 2-phenylacetate

To a stirred solution of 2-methyl-2-phenylacetate (10 g, 1 eq) in dryMeOH was added sulfuric acid (1.0 mL) dropwise and heated to reflux.Stirring was then continued for 2 hours. The reaction mixture was thencooled and poured into saturated aqueous NaHCO₃ and extracted withEtOAc. The combined organic fractions were dried over Na₂SO₄, filtered,and concentrated under reduced pressure to yield an oil (10.5 g, 95%)that was not further purified.

Methyl 3-methyl-2-phenylbutanoate

To a stirred solution of methyl 3-methyl-2-phenylbutanoate (0.5 g, 1 eq)in dry THF was added HMPA (1 eq), LiHMDS (1 eq), and 2-bromopropane at−40 to 0° C. for 1 h. The reaction mixture was quenched with water andextracted with EtOAc. The combined organic fractions were dried overNa₂SO₄, filtered, and concentrated under reduced pressure to yield anoil that that was purified by column chromatography using silica gel toprovide the product (0.24 g, 34%).

3-Methyl-2-phenylbutanehydrazide

A stirred solution of methyl 3-methyl-2-phenylbutanoate (0.87 g, 1 eq)and hydrazine hydrate (10 mL) was heated at 110° C. for 12 h. Thereaction mixture was then cooled and the solvents removed under reducedpressure. The crude oil was diluted with EtOAc and washed with H₂O andthe organic phase dried over Na₂SO₄, filtered, and the solvents removedunder reduced pressure to yield a yellow oil (0.17 g, 47%) that waspurified by column chromatography over silica gel to yield the product(0.61 g).

(E)-N′-(3,4-Dimethoxybenzylidene)-3-methyl-2-phenylbutanehydrazide

(E)-N′-(3, 4-Dimethoxybenzylidene)-3-methyl-2-phenylbutanehydrazide wassynthesized from 3-methyl-2-phenylbutanehydrazide according to themethod used for the preparation of Example 1. The product (9-1) waspurified by column chromatography over silica gel using ethylacetate/hexanes to provide a solid (0.109 g, 10% yield).

Example 10 Synthesis of (E)-N′-(3,4-Dimethoxybenzylidene)-2-methoxy-N-methyl-2-phenylacetohydrazide

(E)-N′-(3,4-Dimethoxybenzylidene)-2-methoxy-N′-methyl-2-phenylacetohydrazide(12-70) was synthesized according to the method used for the preparationof Example 6. To a solution of(E)-N′-(3,4-dimethoxybenzylidene)-2-methoxy-2-phenylacetohydrazide(12-21) (0.56 g) in anhydrous DMF in an oven-dried flask under argon wasadded iodomethane (1 eq) then NaH (60% in oil; 1.1 eq) was added and themixture stirred for 2 hours. The reaction was quenched with brine andfurther diluted with water. The aqueous mixture was extracted with EtOAcand the combined organics were washed with water three times, brineonce, dried over Na₂SO₄ and concentrated in vacuo. Purification bychromatography provided the product (12-70) (0.4 g, 70%).

Example 11 Synthesis of(E)-2-(4-(1H-pyrazol-1-yl)phenyl)-N-(4-bromo-3,5-dimethoxybenzylidene)-2-methoxy-N-(2,2,2-trifluoroethyl)acetohydrazide

To a solution of(E)-2-(4-(1H-pyrazol-1-yl)phenyl)-N-(4-bromo-3,5-dimethoxybenzylidene)-2-methoxyacetohydrazide(0.167 g, 0.35 mmol) in anhydrous DMF (3.0 mL) was added a 60%dispersion of NaH in mineral oil (0.017 g, 0.43 mmol) under argon andstirred for 10 min. 1,1,1-trifluoro-3-iodopropane (0.042 mL, 0.43 mmol)was added and the mixture was stirred at room temperature for 24 hoursthen heated to 100° C. for 10 days and then additional1,1,1-trifluoro-3-iodopropane (0.042 mL, 0.43 mmol) added and thereaction heated to 150° C. for 1 hour. After cooling to roomtemperature, the mixture was diluted with water and brine and extractedwith EtOAc times. The combined organics were washed with brine, driedover Na₂SO₄ and concentrated in vacuo. Purification by chromatography(20-50% EtOAc-hexanes) gave of product (11-1) as a light yellow solid(0.0543 g, 28% yield).

Example 12 Synthesis of Further Representative Compounds

The following representative compounds in Table 1 were synthesizedaccording to (i) the foregoing procedures by selecting appropriatestarting materials (for example, 4-fluoro mandelic acid derivatives(e.g., examples 12-1 and 12-3) were synthesized using commerciallyavailable 4-fluoromandelic acid) and (ii) known organic synthesistechniques (for example, treatment of commercially availableα-phenylacetic acid methyl ester with hydrazine hydrate in ethanol underwith heating provides phenyl-acetic acid hydrazide (see, e.g., Pandeye,S. N.; Manjula, H.; Stables, J. P.; Pharmazie; 2001, 56, 121-124) andtreatment of phenyl acetic acid hydrazide with a substitutedbenzaldehyde in ethanol with heating and in the presence of catalyticacetic acid provides the corresponding substituted phenyl-acetic acidbenzylidenehydrazide (see, e.g., Stephanidou-Stephanatou, J.;Lefkopoulou, S; Journal of Heterocyclic Chemistry; 1982; 19;705-711.0)).

TABLE 1 Example No. Structure MW 1-1

408.168 2-1

416.158 3-1

404.174 4-1

344.433 5-1

492.23 6-1

409.44 7-1

401.46 8-1

414.12 9-1

340.42 11-1

555.34 12-1 

424.043 12-2 

454.029 12-3 

424.043 12-4 

440.014 12-5 

410.08 12-6 

396.064 12-7 

376.119 12-8 

346.108 12-9 

400.43 12-10

362.103 12-11

350.083 12-12

440.014 12-13

408.168 12-14

387.099 12-15

392.83 12-16

414.139 12-17

358.39 12-18

432.205 12-19

358.39 12-20

312.37 12-21

328.368 12-22

357.088 12-23

378.158 12-24

344.37 12-25

328.37 12-26

356.42 12-27

399.169 12-28

370.49 12-29

328.37 12-30

358.39 12-31

391.23 12-32

298.34 12-33

326.40 12-34

336.31 12-35

314.41 12-36

337.21 12-37

314.34 12-38

311.38 12-39

298.34 12-40

300.31 12-41

420.46 12-42

418.08 12-43

500.095 12-44

464.058 12-45

452.195 12-46

434.124 12-47

478.074 12-48

500.095 12-49

464.058 12-50

420.109 12-51

386.148 12-52

374.128 12-53

329.36 12-54

337.21 12-55

458.31 12-56

409.44 12-57

458.31 12-58

458.31 12-59

423.46 12-60

472.33 12-61

409.44 12-62

458.31 12-63

449.095 12-64

404.14 12-65

390.1 12-66

370.15 12-67

424.12 12-68

414.45 12-69

372.42 12-70

342.39 12-71

326.40 12-72

312.37 12-73

342.39 12-74

423.23 12-75

401.26 12-76

372.42 12-77

361.12 12-78

369.35 12-79

372.37 12-80

404.39 12-81

420.84 12-82

465.29 12-83

420.84 12-84

492.36 12-85

447.91 12-86

492.36 12-87

479.32 12-88

430.45 12-89

327.35 12-90

358.39 12-91

363.34 12-92

403.45 12-93

368.36 12-94

296.32 12-95

327.35 12-96

281.29 12-97

327.35 12-98

282.29 12-99

449.52  12-100

435.27  12-101

464.35  12-102

464.35  12-103

400.43  12-104

473.3  12-105

490.1  12-106

539.07  12-107

504.1  12-108

473.06  12-109

507.10  12-110

475.074  12-111

475.1  12-112

492.100  12-113

413.19  12-114

492.4  12-115

520.42  12-116

450.04  12-117

460.074  12-118

443.047  12-119

393.16  12-120

460.074  12-121

386.147  12-122

449.094  12-123

513.126  12-124

387.1793  12-125

449.094  12-126

431.16  12-127

406.052  12-128

414.1790  12-129

478.0738  12-130

430.17  12-131

478.07  12-132

475.11  12-133

400.16  12-134

506.39  12-135

479.33  12-136

473.33  12-137

474.32  12-138

475.31  12-139

462.36  12-140

487.36  12-141

526.41  12-142

501.39  12-143

422.27  12-144

438.48  12-145

487.35  12-146

487.35  12-147

506.39  12-148

506.39  12-149

501.37  12-150

520.42  12-151

501.37  12-152

520.42  12-153

555.34  12-154

464.35  12-155

394.42  12-156

424.45

Example 13 Compound Assay PDE10 Biochemical Assay

The phosphodiesterase (PDE) assay was performed using recombinant humanPDE 1A3, 2A3, 3 catalytic region, 4 catalytic region, 5 catalyticregion, 7A, 8A, 9A2, 10A1 and 11A1 enzymes expressed in a baculoviralsystem using Sf9 cells. PDE activity was measured using a modificationof the two-step method of Thompson and Appleman described above whichwas adapted for 96 well plate format. The effect of the PDE inhibitorswas determined by assaying a fixed amount of the enzyme in the presenceof test compound concentrations and a substrate concentration below thatof the Km, so that Ki equals IC₅₀. The final assay volume was 110 μlwith assay buffer (10 mM MgCl₂; 40 mM Tris.HCl; pH 7.4). Reactions wereinitiated with enzyme and incubated with (³H)-substrate and substancefor 20 minutes at 30° C. The reaction was terminated by denaturing theenzyme (heating the reaction to 70° C. for 2 minutes). The reaction wasthen cooled at 4° C. for 10 minutes before the addition of snake venom(Crotalus atrox, 0.2 mg/ml) for 10 minutes at 30° C., thus allowingnon-specific hydrolysis of the tritiated substrate. Separation of theremaining unhydrolysed cyclic nucleotide was achieved by a batch bindingof the mixture to activated Dowex (200 μl) anion exchange resin. Theanion exchange resin bound the charged nucleotides, leaving onlyhydrolysed (³H) substrate in the soluble fraction. The soluble fraction(50 μl) was then added to microscint-20 (200 μl) and counted on a TopCount Plate reader. Radioactivity units were plotted against inhibitorconcentration and IC₅₀ values obtained using Graph Pad Prism software.

Alternatively, phosphodiesterase activity was measured by scintillationproximity assay (SPA) with [³H]-cGMP as substrate. Purified PDE10 wasdiluted and stored in 25 mM Tris-Cl (pH 8.0)/100 mM NaCl/0.05% Tween20/50% glycerol/3 mM DTT. Assays contained (final concentrations): 50 mMTris-Cl (pH 7.5)/8.3 mM MgCl₂/1.7 mM EGTA/0.5 mg/ml BSA/5% DMSO and 2 ngPDE10 in a final volume of 0.1 mL. Inhibition was evaluated at 8concentrations in duplicate. Reactions were initiated by addition ofenzyme and were terminated after 20 minutes at 30° C. by the addition of50 μl of SPA beads containing Zn⁺⁺. The mixture was shaken, allowed tosettle for 3 hours, and counted in a Wallac plate counter. Results (netcpm) were fitted to a four parameter logistic model using Excel Solver®.

Further, the inhibition of other PDE enzymes by the PDE10 inhibitors wasevaluated under the same conditions described above for PDE10 except theamount of enzyme added was optimized for each PDE. Fractional inhibitionwas evaluated at four concentrations (0.1, 1, 10, and 100 μM). In caseswhere inhibition at the highest concentration was less than 50%, thelower limit value in the logistic model was fixed to 0% activity.

In the above assay, compounds of this invention are PDE10 inhibitorswith an IC₅₀ of 100 μM or less, generally less than 10 μM, and typicallyless than 1 μM. To this end, compounds 1-1, 2-1, 3-1, 4-1, 5-1, 6-1,7-1, 8-1, 9-1, 11-1, 12-1, 12-2, 12-3, 12-4, 12-5, 12-6, 12-7, 12-8,12-9, 12-10, 12-12, 12-13, 12-14, 12-15, 12-16, 12-17, 12-18, 12-19,12-20, 12-21, 12-22, 12-23, 12-24, 12-25, 12-26, 12-41, 12-42, 12-43,12-44, 12-45, 12-46, 12-47, 12-48, 12-49, 12-50, 12-51, 12-52, 12-55,12-56, 12-57, 12-58, 12-59, 12-60, 12-61, 12-62, 12-63, 12-64, 12-65,12-66, 12-67, 12-68, 12-69, 12-70, 12-71, 12-80, 12-82, 12-83, 12-84,12-85, 12-86, 12-87, 12-88, 12-89, 12-90, 12-104, 12-105, 12-107,12-108, 12-109, 12-111, 12-112, 12-114, 12-115, 12-116, 12-117, 12-118,12-119, 12-120, 12-121, 12-122, 12-123, 12-124, 12-125, 12-126, 12-127,12-128, 12-129, 12-130, 12-131, 12-132, 12-133, 12-134, 12-135, 12-136,12-137, 12-138, 12-139, 12-140, 12-141, 12-142, 12-144 and 12-155 forexample, were found to have IC₅₀ values of less than or equal to 1 μM.

Examples 14-15 Evaluation of Representative Compounds in BehavioralModels

Schizophrenia has been associated with dysfunctions of dopaminergic,glutamatergic and serotonergic neurotransmission. Psychostimulant drugsin these three classes, dopaminergic agonists (such as amphetamine andapomorphine), glutamatergic antagonists (such as PCP and ketamine), andserotonergic agonists (such as LSD and MDMA), all induce psychotomimeticstates (e.g., hyperactivity and disruption of prepulse inhibition) inanimals that closely resemble schizophrenia symptoms in humans. Knownantipsychotic drugs, including both typical antipsychotics (e.g.,haloperidol) and atypical antipsychotics (e.g., olanzapine), reversesuch psychotomimetic states in animals. Examples 14-15 described belowevaluate representative compounds of the present invention in animalbehavioral models to compare the resulting effect to that of knownantipsychotics. Methods used in the Examples 14-15 are as follows.

Psychostimulant-induced hyperactivity is measured by injecting animalswith PCP and monitoring the animals' activity levels in the VersaMaxchambers (Accuscan Instruments, Columbus, Ohio) measuring 40×40 cm.Locomotor activity is detected by photobeam breaks as the animal crosseseach beam. The animal is placed in the center of the field and leftundisturbed for a period of time (20 min to 2 hr) to measure itsspontaneous activity in a novel environment. Measurements used to assesslocomotor activity include: horizontal activity, total distancetraveled, vertical activity (rearing events—animal raises up onhindlimbs), rotation, stereotypy, and distance traveled in the centercompared to total distance traveled (center: total distance ratio). TheNMDA antagonist PCP induces psychosis-like conditions manifested ashyperactivity and increased stereotypic behavior. Known antipsychoticsare able to reverse psychostimulant-induced hyperactivity and increasedstereotypy.

Conditioned avoidance response (CAR) is a behavioral test to evaluateantipsychotic effect of a test compound. It utilizes a shuttle box (MedAssociates, St. Albans, Vt.) with two equal chambers separated by aretractable door. Each chamber is fitted with metal grid floor that iscapable of delivering electric shocks independently. A computer programis used to implement the testing paradigm as well as record the animal'smovement between the two chambers through infrared beam sensors. Thetesting paradigm is as the follows. A mouse is placed into one chamber.A light (conditioned stimulus, CS) comes on. Five seconds later, mildelectric shocks (0.4 mA) (unconditioned stimulus, US) are delivered tothe chamber where the mouse is located (as detected by infrared beams)until the mouse escapes to the adjacent chamber or until 10 sec haselapsed. The US and CS always co-terminate. With randomized inter-trialintervals averaging 15 sec, 30 such CS-US pairing trials are given toeach mouse each day. For each trial, an escape response is registered ifthe mouse crosses to the other chamber after being shocked (i.e., duringthe 10-sec US period), and an avoidance response is registered if themouse crosses to the other chamber during the first 5-sec CS onlyperiod. The animals are trained in such paradigm for 15-20 days, duringwhich the average percentage of avoidance responses will improve to60-80%. This indicates that animals have learned to avoid the onset offootshocks by moving to the opposite chamber upon activation of the CS(light). These trained animals are then used for compound testing usingthe same paradigm. Known antipsychotics have been found to inhibit theconditioned avoidance response, and the ability of new compounds toinhibit this response is thought to be predictive of antipsychoticeffect in humans.

Example 14 Reduction of PCP-Induced Hyperactivity

Compounds 12-63, 12-55 and 12-60 of the present invention (as identifiedin Table 1 of Example 12) were evaluated for the ability tosignificantly and substantially reduce PCP-induced hyperactivity.C57BL/6 male mice were injected with either compound (10 mg/kg) orvehicle via i.p. Ten minutes later, the mice were injected with PCP (5mg/kg) via i.p. The mice were placed in the activity chambers 10 minutesafter PCP injection and their locomotor activities were monitored byinfrared beam breaks for 20 min. FIG. 1 shows that Compound 12-63significantly reduced the hyperactivity elicited by PCP compared tovehicle (p<0.0001, n=8 per group, repeated measures ANOVA). FIG. 2 showsthat Compound 12-55 (10 mg/kg, i.p.) also substantially reduceshyperactivity (p=0.0008 compared to vehicle, n=8 per group, repeatedmeasures ANOVA) and FIG. 3 shows a similar result with Compound 12-60(p<0.0001 compared to vehicle, n=8 per group, repeated measures ANOVA).

Example 15 Reduction of Conditioned Avoidance Response

Compound 12-44 of the present invention (as identified in Table 1 ofExample 12) was evaluated for the ability to reduce ConditionedAvoidance Response after oral dosing, as shown in FIG. 4. C57BL/6 malemice were trained in the CAR paradigm to predict and avoid the noxiousstimulus, reaching a plateau of approximately 20-25 avoidance responsesper 30 trials (“training plateau”) each day. The mice were then injectedwith either compound or vehicle via i.p., and 20 minutes later they weretested for 30 trials in the CAR paradigm. Vehicle treatment and compoundtreatment were given to the same animals on alternating days, and theeffect of compound in reducing avoidance response was analyzed throughwithin-subject comparison (paired t-test). Vehicle exposure (“vehicle”)does not alter the avoidance response of these trained animals. FIG. 4shows that Compound 12-44 significantly reduces the number of avoidanceresponses at oral doses of both 10 mg/kg (p=0.01, n=6 per group, pairedt-test) and 30 mg/kg (p=0.001, n=6 per group, paired t-test). At thelatter dose, the number of avoidances is substantially reduced from 28to 7.

Example 16 Reduction of PCP-Induced Hyperactivity by Compound 12-63

Compound 12-63 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 5A. C57BL/6 male micewere administered either compound or vehicle via oral gavage. Fifteenminutes later, the mice were injected with PCP (5 mg/kg) via the i.p.route. The mice were placed in activity chambers 10 minutes after PCPinjection, and their locomotor activity in the horizontal dimension wasmonitored by infrared beam breaks for 20 min (5 consecutive 4-minuteintervals (INT) as indicated). FIG. 5A shows that Compound 12-63 (4 and10 mg/kg) reduces or abolishes the hyperactivity induced by PCP comparedto the vehicle+PCP control group (p=0.00003 for 10 mg/kg dose, n=8 pergroup, paired t-test).

Example 17 Reduction of Conditioned Avoidance Response by Compound 12-63

Compound 12-63 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 5B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials (“training plateau”). The mice werethen given either vehicle (15 minutes prior to testing) or compound (25minutes prior to testing) via oral gavage, and were tested for 30 trialsin the CAR paradigm. Vehicle treatment and compound treatment were givento the same animals on alternating days, and the effect of compound inreducing avoidance response was analyzed through within-subjectcomparison (paired t-test). Vehicle exposure (“vehicle”) does not alterthe avoidance response of these trained animals. FIG. 5B shows thatCompound 12-63 (10 mg/kg) significantly reduces the number of avoidanceresponse (p=0.007, n=6 per group). In all these cases, the number ofescape responses increased correspondingly and the total numbers oftransitions between the two chambers did not change (data not shown),indicating a specific reduction of CAR that is not due to compromisedmotor function.

Example 18 Reduction of PCP-Induced Hyperactivity by Compound 12-104

Compound 12-104 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 6A. C57BL/6 male micewere administered either compound or vehicle via oral gavage.Twenty-five minutes later, the mice were injected with PCP (5 mg/kg) viathe i.p. route. The mice were placed in activity chambers 10 minutesafter PCP injection and their locomotor activity in the horizontaldimension was monitored by infrared beam breaks for 20 min (5consecutive 4-minute intervals (INT) as indicated). FIG. 6A shows thatCompound 12-104 (3 and 6 mg/kg) reduces or abolishes the hyperactivityinduced by PCP, as seen by comparison with the vehicle+PCP control(p=0.0189, n=8 per group, independent sample t-test).

Example 19 Reduction of Conditioned Avoidance Response by Compound12-104

Compound 12-104 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 6B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials each day. The mice were then giveneither vehicle (15 minutes prior to testing) or compound (25 minutesprior to testing) via oral gavage, and then were tested for 30 trials inthe CAR paradigm. Vehicle treatment and compound treatment were given tothe same animals on alternating days, and the effect of compound inreducing avoidance response was analyzed through within-subjectcomparison (paired t-test). Vehicle exposure (“vehicle”) does not alterthe avoidance response of these trained animals. FIG. 6B shows thatCompound 12-104 (10 and 30 mg/kg) significantly reduces the number ofavoidance response (p=0.0159, n=7 per group).

Example 20 Reduction of PCP-Induced Hyperactivity by Compound 12-114

Compound 12-114 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 7A. C57BL/6 male micewere given either compound or vehicle by oral gavage. Twenty-fiveminutes later they were injected with PCP (5 mg/kg, i.p.). Ten minuteslater, the mice were placed in activity chambers, and their locomotoractivity in the horizontal dimension was monitored by infrared beambreaks for 20 min (5 consecutive 4-minute intervals (INT) as indicated).FIG. 7A shows that Compound 12-114 (10 mg/kg) completely abolishes thehyperactivity induced by PCP, as seen by comparison to the vehicle+PCPcontrol (p<0.0000001, n=8 per group, independent sample t-test).

Example 21 Reduction of Conditioned Avoidance Response by Compound12-114

Compound 12-114 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 7B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials each day. The mice were then giveneither vehicle (15 minutes prior to testing) or compound (25 minutesprior to testing) via oral gavage, and then were tested for 30 trials inthe CAR paradigm. Vehicle treatment and compound treatment were given tothe same animals on alternating days, and the effect of compound inreducing avoidance response was analyzed through within-subjectcomparison (paired t-test). Vehicle exposure (“vehicle”) does not alterthe avoidance response of these trained animals. FIG. 7B shows thatCompound 12-114 (10 mg/kg) significantly reduces the number of avoidanceresponse (p=0.0003, n=7 per group, paired t-test).

Example 22 Reduction of PCP-Induced Hyperactivity by Compound 12-132

Compound 12-132 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 8A. C57BL/6 male micewere co-injected with PCP (5 mg/kg) and either compound or vehicle viathe i.p. route. Ten minutes later, the mice were placed in activitychambers and their locomotor activity in the horizontal dimension wasmonitored by infrared beam breaks for 20 min (5 consecutive 4-minuteintervals (INT) as indicated). FIG. 8A shows that Compound 12-132 (10mg/kg) substantially reduces the hyperactivity induced by PCP as seen bycomparison to the vehicle+PCP control (p<0.0000001, n=8 per group,paired t-test).

Example 23 Reduction of Conditioned Avoidance Response by Compound12-132

Compound 12-132 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 8B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials (“training plateau”). The mice werethen given either vehicle (15 minutes prior to testing) or compound (25minutes prior to testing) via oral gavage, and were then tested for 30trials in the CAR paradigm. Vehicle treatment and compound treatmentwere given to the same animals on alternating days, and the effect ofcompound in reducing avoidance response was analyzed throughwithin-subject comparison (paired t-test). Vehicle exposure (“vehicle”)does not alter the avoidance response of these trained animals. FIG. 8Bshows that Compound 12-132 (10 mg/kg) significantly reduces the numberof avoidance response (p=0.044, n=7 per group). In all these cases, thenumber of escape responses increased correspondingly and the totalnumbers of transitions between the two chambers did not change (data notshown), indicating a specific reduction of CAR that is not due tocompromised motor function.

Example 24 Reduction of PCP-Induced Hyperactivity by Compound 12-134

Compound 12-134 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 9A. C57BL/6 male micewere administered either compound or vehicle via oral gavage.Twenty-five minutes later, the mice were injected with PCP (5 mg/kg) viathe i.p. route. The mice were placed in the activity chambers 10 minutesafter PCP injection and their locomotor activity in the horizontaldimension was monitored by infrared beam breaks for 20 min (5consecutive 4-minute intervals (INT) as indicated). FIG. 9A shows thatCompound 12-134 (4, 6 and 10 mg/kg) reduces or abolishes thehyperactivity induced by PCP, as seen by comparison with the vehicle+PCPcontrol (p=0.0033, 0.0012, and 0.00001, respectively, n=8 per group,independent sample t-test).

Example 25 Reduction of Conditioned Avoidance Response by Compound12-134

Compound 12-134 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 9B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials each day. The mice were then giveneither vehicle (15 minutes prior to testing) or compound (25 minutesprior to testing) via oral gavage, and then were tested for 30 trials inthe CAR paradigm. Vehicle treatment and compound treatment were given tothe same animals on alternating days, and the effect of compound inreducing avoidance response was analyzed through within-subjectcomparison (paired t-test). Vehicle exposure (“vehicle”) does not alterthe avoidance response of these trained animals. FIG. 9B shows thatCompound 12-134 (3, 6, and 10 mg/kg) significantly reduces the number ofavoidance response (p=0.0117, 0.0043, and 8E-9, respectively, n=7 pergroup).

Example 26 Reduction of PCP-Induced Hyperactivity by Compound 12-115

Compound 12-115 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 10A. C57BL/6 malemice were administered either compound or vehicle via oral gavage.Twenty-five minutes later, the mice were injected with PCP (5 mg/kg) viathe i.p. route. The mice were placed in the activity chambers 10 minutesafter injection and their locomotor activity in the horizontal dimensionwas monitored by infrared beam breaks for 20 min (5 consecutive 4-minuteintervals as indicated). FIG. 10A shows that Compound 12-115significantly reduces hyperactivity at doses of 2 and 5 mg/kg p.o.(p=0.02 and 0.001, respectively), and abolishes hyperactivity at a p.o.dose of 10 mg/kg (p=1.5 E-5, n=8 per group, independent sample t-test).

Example 27 Reduction of Conditioned Avoidance Response by Compound12-115

Compound 12-115 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 10B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials each day. The mice were then giveneither vehicle (15 minutes prior to testing) or compound (25 minutesprior to testing) via oral gavage, and were tested for 30 trials in theCAR paradigm. Vehicle treatment and compound treatment were given to thesame animals on alternating days, and the effect of compound in reducingavoidance response was analyzed through within-subject comparison(paired t-test). Vehicle exposure (“vehicle”) does not alter theavoidance response of these trained animals. FIG. 10B shows thatCompound 12-115 (10 mg/kg, p.o.) significantly reduces the number ofavoidance response (p=1.2 E-5, n=7 per group, paired t-test).

Example 28 Reduction of PCP-Induced Hyperactivity by Compound 12-140

Compound 12-140 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 11A. C57BL/6 malemice were administered either compound or vehicle via oral gavage.Twenty-five minutes later, the mice were injected with PCP (5 mg/kg) viathe i.p. route. The mice were placed in the activity chambers 10 minutesafter PCP injection and their locomotor activity in the horizontaldimension was monitored by infrared beam breaks for 20 min (5consecutive 4-minute intervals (INT) as indicated). FIG. 11A shows thatCompound 12-140 significantly reduces or abolishes hyperactivity atdoses of 4 and 8 mg/kg p.o. (p=0.004 and 5.9 E-8, respectively, n=8 pergroup, independent sample t-test).

Example 29 Reduction of Conditioned Avoidance Response by Compound12-140

Compound 12-140 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 11B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials each day. The mice were then giveneither vehicle (15 minutes prior to testing) or compound (25 minutesprior to testing) via oral gavage, and were tested for 30 trials in theCAR paradigm. Vehicle treatment and compound treatment were given to thesame animals on alternating days, and the effect of compound in reducingavoidance response was analyzed through within-subject comparison(paired t-test). Vehicle exposure (“vehicle”) does not alter theavoidance response of these trained animals. FIG. 11B shows thatCompound 12-140 at doses of 6 and 10 mg/kg significantly reduces thenumber of avoidance response (p=0.00053 and 3.1 E-12, respectively, n=7per group, paired t-test).

Example 30 Reduction of PCP-Induced Hyperactivity by Compound 12-142

Compound 12-142 (as identified in Table 1 of Example 12) was found toreduce PCP-induced hyperactivity, as shown in FIG. 12A. C57BL/6 malemice were administered either compound or vehicle via oral gavage.Twenty-five minutes later, the mice were injected with PCP (5 mg/kg) viathe i.p. route. The mice were placed in the activity chambers 10 minutesafter PCP injection and their locomotor activity in the horizontaldimension was monitored by infrared beam breaks for 20 min (5consecutive 4-minute intervals (INT) as indicated). FIG. 12A shows thatCompound 12-142 essentially abolishes hyperactivity at a dose of 8 mg/kgp.o. (p=5.9 E-6, n=8 per group, independent sample t-test).

Example 31 Reduction of Conditioned Avoidance Response by Compound12-142

Compound 12-142 (as identified in Table 1 of Example 12) was found toreduce Conditioned Avoidance Responses (CAR), as shown in FIG. 11B.C57BL/6 male mice were trained in the CAR paradigm to predict and avoidthe noxious stimulus (foot shock), reaching a plateau of approximately25 avoidance responses per 30 trials each day. The mice were then giveneither vehicle (15 minutes prior to testing) or compound (25 minutesprior to testing) via oral gavage, and were tested for 30 trials in theCAR paradigm. Vehicle treatment and compound treatment were given to thesame animals on alternating days, and the effect of compound in reducingavoidance response was analyzed through within-subject comparison(paired t-test). Vehicle exposure (“vehicle”) does not alter theavoidance response of these trained animals. FIG. 11B shows thatCompound 12-142 at a dose of 5 mg/kg significantly reduces the number ofavoidance response (p=0.033, n=7 per group, paired t-test).

It will be appreciated that, although specific embodiments of theinvention have been described herein for purposes of illustration,various modifications may be made without departing from the spirit andscope of the invention. Accordingly, the invention is not limited exceptas by the appended claims.

1-70. (canceled)
 71. A compound having the following structure (III):

or a pharmaceutically acceptable salt, stereoisomer, solvate or prodrugthereof, wherein: R₁ is C₁₋₆alkyl, C₁₋₆haloalkyl,—(CH₂)_(n)O(CH₂)_(m)CH₃ or —(CH₂)_(n)N(CH₃)₂; R₂ and R₃ are the same ordifferent and independently substituted or unsubstituted heterocyclyl,or substituted or unsubstituted aryl; and R₄ and R₅ are the same ordifferent and independently hydrogen, C₁₋₆alkyl or C₁₋₆haloalkyl; n is1, 2, 3, 4, 5 or 6; and m is 0, 1, 2, 3, 4, 5 or
 6. 72. The compound ofclaim 71 wherein R₄ and R₅ are the same or different and independentlyhydrogen or C₁₋₆alkyl.
 73. The compound of claim 71 wherein R₄ and R₅are hydrogen.
 74. The compound of claim 71 wherein R₁ is C₁₋₆alkyl. 75.The compound of claim 74 wherein R₁ is methyl.
 76. The compound of claim74 wherein R₁ is ethyl.
 77. The compound of claim 74 wherein R₁ isisopropyl.
 78. The compound of claim 71 wherein R₃ is substitutedphenyl.
 79. The compound of claim 78 wherein R₃ is3,4,5-trimethoxyphenyl.
 80. The compound of claim 78 wherein R₃ is4-bromo-3,5-dimethoxyphenyl.
 81. The compound of claim 71 wherein R₂ issubstituted or unsubstituted phenyl.
 82. The compound of claim 81wherein R₂ is 4-morpholinophenyl.
 83. The compound of claim 81 whereinR₂ is 4-(1H-pyrazol-1-yl)phenyl.
 84. The compound of claim 71 wherein R₂is substituted or unsubstituted naphthyl.
 85. The compound of claim 71wherein R₂ is substituted or unsubstituted heteroaryl.
 86. Apharmaceutical composition comprising a compound of claim 71 and apharmaceutically acceptable carrier or diluent. 87-100. (canceled)